The present invention relates to an analog-digital optical conversion process and apparatus.
It is known to construct an analog-digital coder by using electronic circuits. However, integrated optics techniques make it possible to carry out signal processing operations with comparable performance levels to those in electronics. Thus, it is known to produce an analog-digital coder using the properties of the integrated optics amplitude modulator. This amplitude modulator is the integrated version of a Mach-Zendler-type two-wave interferometer. In such an interferometer, the light intensity transmitted varies sinusoidally as a function of the phase shift created between the two arms of the interferometer. This phase shift can be obtained by applying a potential difference between electrodes positioned on either side of wavelengths. In such an analog-digital coder, the number of modulators corresponds to the number of bits of the output word. The signal to be digitized is applied to the electrodes respectively corresponding to all these modulators.
On considering a Gray coding system, this imposes the same absolute precision for each transition, so that the relative precision increases in proportion to the significance of the bit of the output word, which can be a dynamics limitation.